Electrical relay



y 1932- B. E. OHAGAN 1,858,966

ELECTRICAL RELAY Filed Dec. 5, 1930 Patented May 17, 1932 UNITED STATES PATENT OFFICE BERNARD E. OI-IAGAN, 0F SWISSVALE, PENNSYLVANIA, ASSIGNOR TO THE UNION SWITCH & SIGNAL COIv'IPANY, O1 SWISSVALE, PENNSYLVANIA, A CORPORATION OF PENNSYLVANIA ELECTRICAL RELAY Application filed December 5, 1930. Serial No. 500,296.

My invention relates to electrical relays, and has for an object the provision of means for compensating such relays for changes of temperature, so that the armature will be moved to the attracted position at substantially the same voltage applied to the operating winding, regardless of the temperature to which the relay is exposed.

The operating winding of a relay is ordinarily made of copper wire, and this wire has a positive temperature resistance coefficient, so that as the temperature increases, the resistance also increases. The result of this is, that for a constant applied voltage the current in the operating winding decreases with increase of temperature. Inasmuch as the factor which determines the pick-up of the relay armature is ampere turns, it follows that if the armature torque is constant, the armature will pick up at a lower voltage when the temperature is low than when the temperature is high. In accordance with my invention I have provided means for decreasing the armature torque with increase of temperature, so that the armature will pick up at substantially the same applied voltage regardless of temperature.

I will describe two forms of relays embodying my invention, and will then point out the novel features thereof in claims.

In the accompanying drawings, Fig. 1 is view showing in side elevation one form of relay embodying my invention. Fig. 2 is a similar view, showing a modified form of relay embodying my invention.

Similar reference characters refer to similar parts in each of the views.

Referring first to Fig. 1, the relay comprises a core 2 provided with an operating winding 3, and an armature 4 pivotally mounted at point 8 and biased to a retracted position. Attached to the armature 4 is a bracket 6 which carries a weight 5, and interposed between the bracket and the weight, is a bimetallic strip 7 which changes its shape in response to changes of temperature. The parts are so adjusted that as the temperature increases the weight 5 is shifted to the left, thereby decreasing the torque exerted by this weight on the armature 4. Conversely, as the temperature decreases, the strip 7 bends so that the weight 5 is shifted to the right, hereby increasing the torque exerted by this weight on the armature.

For any given voltage applied to the terminals of winding 3, as the temperature increases, the current flowing in this winding decreases, but at the same time the torque exerted by the weight 5 on the armature 4: also decreases, so that the armature will be attracted at a given voltage regardless of the temperature.

Referring now to Fig. 2, the relay which is here shown, is of the telephone type comprising a core 2 provided with an operating winding 3, and an armature 4 pivotallymounted at 8. This armature is biased to the retracted position by a contact member 9 which is in the form of a bi-m-etallic strip, and coacting with this member 9 is a second contact member 10. The parts are so adjusted that for all temperatures in the range to which the relay is exposed, contact 910 is closed when the armature is in its retracted position, but that the biasing force exerted on the armature by the contact member 9 decreases as the surrounding temperature in creases. It follows that the relay may be so adjusted that the armature 42 will be moved to its attracted position to open contact 910 when a given voltage is applied to the winding 3 regardless of the surrounding temperature.

Relays embodying my invention are particularly useful in battery char ing systems. In systems of this character it is common practice to provide a relay which is open or released when the charge in a storage battery is below normal, but which closes when the charge in the battery reaches the normal value. These relays must be highly sensi tive, in that they must close at a given applied voltage, regardless of the temperature to which the relay is exposed, and relays embodyin g my invention are capable of meeting this requirement.

Although I have herein shown and de scribed only two forms of relays embodying my invention, it is understood that various changes and modifications may be made therein within the scope of the appended claims without departing from the spirit and scope of my invention.

5 Having thus described my invention, what I claim is:

1. A relay comprising an operating winding having a positive temperature resistance coefficient, a pivoted armature, a weight attached to said armature, and a lei-metallic strip interposed between said armature and said weight to decrease the torque due to said weight in response to increase of temperature.

2. A relay comprising an operating winding having a positive temperature resistance eoeflicient, a pivoted armature, a weight, and means including a iii-metallic strip for at taching said weight to said armature and for shifting the position of the weight relative to the pivotal axis of the armature, whereby the torque on the armature due to the weight varies in response to variations in temperature.

In testimony whereof I afiix my signature.

BERNARD E. OHAGAN. 

